Six presidential candidates spent $15,000 each for the privilege of speaking at the Iowa Republican Party’s Ames straw poll and reserving space for their supporters. On Saturday, the GOP state central committee will decide which of the other candidates, who haven’t paid a penny, will get their names on the ballot, too.

I talked with a few central committee members this week, who said they think it’s a tough decision. For example, should the committee include not-yet-announced candidate Rick Perry, who seems to be moving toward running? What about Sarah Palin?

Should announced candidates who have chosen not to buy space for the straw poll — Mitt Romney, Jon Huntsman and Newt Gingrich, for example — get a spot on the ballot?

“Imagine if a candidate who wasn’t there somehow beat a candidate who was there. Yikes,” said central committee member David Fischer, who is affiliated with the campaign of Texas Rep. Ron Paul.

The six candidates who have purchased space at the poll are Paul, Michele Bachmann, Herman Cain, Thaddeus McCotter, Tim Pawlenty and Rick Santorum.

It’s easy to imagine either Palin or Perry becoming the story out of the straw poll, overshadowing candidates who have worked hard and spent a lot of money. In past years, the field has seemed far more established before the August event. This year, the potential for high-profile latecomers adds weight to the decision of whom to include. The committee’s choice may give some insight into how the ultimate party insiders view the likelihood that either Palin or Perry will actually run.

The committee has in the past included announced candidates who haven’t paid for space. In 2007, John McCain and Rudy Giuliani were in the race but decided not to campaign for the straw poll. The committee added their names to the ballot, as well as that of Sen. Fred Thompson, who was within weeks of officially announcing his candidacy.

Candidates who show up for the poll generally — but not always — do better than those who skip it. But in 2007, all three of those no-show candidates beat one who paid for space at the poll: Illinois businessman John Cox. Gosh, it would be pretty embarrassing for Santorum or Cain if Romney beat him without setting foot in Hilton Coliseum.

The debate sponsored by the Iowa Republican Party and Fox News, which will include Romney, Huntsman and Gingrich, raises the stakes for the straw poll. If one of those candidates dominates the Aug. 11 debate, he could turn the heads of undecided straw poll voters on Aug. 13. It’s not unheard of for straw poll voters to accept a free ticket from one candidate but end up voting for another who seems to have more juice at the moment.

Fischer said he hasn’t formed an opinion about who should be on the ballot. He said he has heard some concern among Republicans generally that the straw poll wouldn’t be a valid test if Romney, for example, were excluded.

Former Minnesota Gov. Tim Pawlenty, campaigning in Marshalltown on Tuesday, said he wasn’t aware of the rules for who can be on the ballot. He’s trying to better his position from seventh place in the Des Moines Register Iowa Poll in June to closer to the top of the pack. “I think we’re working harder than Iowa than anyone in the field and I think that’s going to result in good progress for us going into Ames,” he said.

Trudy Caviness, a state central committee member from Ottumwa, said she thinks nationally known and announced candidates like Romney and Huntsman should be on the ballot. A harder decision, she said, is how to treat lesser-known candidates who are officially in the race. There are over 80 candidates who have filed paperwork to run for president. Caviness said she believes poll standing has provided a cutoff in the past.

The central committee has open meetings, but may go into closed session to debate the ballot decision. Note: This is a clarification from the original version, that says the debate will be behind closed doors. Committee members should consider a public debate, and not just because it’s bound to be a fascinating discussion. Decisions like these should be as transparent as possible. If the debate is not open, it will be up to party leaders to explain how the committee arrived at its choices.